a) Kiwi's returning to NZ
b) fewer kiwis departing and
c) people moving to NZ from other lands.
Here are some stats courtesy of Dompost via Stuff and presumably Statistics NZ:
A continued influx of people is boosting New Zealand's population.
Permanent and long-term migration statistics for the year to June show a net gain of 12,500 people, more than double the year to June 2008.
Arrivals were up 4 per cent while departures were down 6 per cent, creating a large influx of new residents.
Net migration to Australia had decreased in the past five months, from the record exodus of December and January.
In the year to June, 42,200 people left for Australia while 13,600 went the other way, two-thirds of them returning Kiwis.
TD Securities senior strategist Annette Beacher said though the actual numbers were small, it was the net growth that counted.
"It doesn't matter if it is people arriving, or residents not leaving, the bottom line is increased population to spend, invest and shore up activity."
The three-month average for population growth was the highest it had been since late 2003, Ms Beacher said. "The combination of improved [housing] affordability and rising population, if it continues, are providing fodder for a solid housing recovery this time next year."
ASB economist Jane Turner said the rising net migration would help provide a floor on demand for housing and retail spending, two sectors at a particularly weak point. "We expect net migration to peak at around 25,000 people per annum over the next year."
The Reserve Bank would see migration as one positive factor for the economy and a potential source of inflationary pressure, she said.